1. Field of the Invention
The present invention relates to the field of computer networking, specifically to the field of local area network communications. More specifically, the present invention relates to methods and apparatus providing for switching of packets locally when the packets are provided from a local source device and destined for a local destination device and providing for asynchronous transfer mode (ATM) switching when packets are provided from a local source device and destined for a remote destination device.
2. Description of the Related Art
U.S. Pat. No. 5,408,469 (the '469 patent) titled “Roping Device Utilizing an ATM switch as a multi-channel backplane in a Communication Network” (which patent is assigned to the assignee of the present invention) describes a device for switching packets received from a local area network segment though an ATM switch to another local area network segment. The '469 patent is incorporated herein by reference. In the background section of the '469 patent there is basic teaching of ATM networks, ATM cell formats, ATM switching and network concentrators and that information is not repeated here. Rather, reference is simply made to the '469 patent.
U.S. Pat. No. 5,420,858 (the '858 patent) titled “Method and Apparatus for communication from a non-ATM communication medium to an ATM communication medium” (which patent is assigned to the assignee of the present invention) describes a device for switching packets received from a local area network segment onto an ATM network. The '858 patent is incorporated herein by reference. In the background section of the '858 patent, there is also disclosure of basic information regarding ATM networks.
In the '469 patent, it is taught that a packet may be received from one local area network (LAN) segment by the central device 200 on a port such as port 211A. The packet is then segmented and ATM cells are formed and provided to the ATM switch. The cells are then switched or routed by the ATM switch, reassembled into a packet and are provided out over another port onto another LAN segment.
While the '469 patent effectively provides for switching of packets over an ATM switch (after segmentation), it does so by segmenting all packets received and then switching the resulting cells over the ATM backplane. This architecture makes it necessary to convert or segment all packets into cells, and to use bandwidth on the ATM backplane for all packets.
The '858 patent, similar to the '469 patent teaches a device in which all packets are segmented and then switched over an ATM network.
What is desired is a system that provides for local switching of packets which are received on a local LAN segment and which are destined for a local LAN segment avoiding the overhead associated with segmentation of all packets.
It is worthwhile mentioning that the local LAN segments may be, for example, token ring, FDDI, Ethernet or other carrier sense multiple access (CSMA) or other local area network protocols. As these protocols are well-known, they will not be described here in detail.